A phosphoenzyme mimic, overlapping catalytic sites and reaction coordinate motion for human NAMPT.
Proceedings of the National Academy of Sciences of the United States of America
confidence
Key findings
Structural study of human NAMPT with ligands; no clinical or biological endpoints reported.
View source on PubMed (PMID 19666527) ↗
- Population
- In vitro human NAMPT enzyme (structural study)
- Blinding
- not_reported
- Controls
- not_reported
- Drug class
- coenzyme
Full abstract
Nicotinamide phosphoribosyltransferase (NAMPT) is highly evolved to capture nicotinamide (NAM) and replenish the nicotinamide adenine dinucleotide (NAD(+)) pool during ADP-ribosylation and transferase reactions. ATP-phosphorylation of an active-site histidine causes catalytic activation, increasing NAM affinity by 160,000. Crystal structures of NAMPT with catalytic site ligands identify the phosphorylation site, establish its role in catalysis, demonstrate unique overlapping ATP and phosphoribosyltransferase sites, and establish reaction coordinate motion. NAMPT structures with beryllium fluoride indicate a covalent H247-BeF(3)(-) as the phosphohistidine mimic. Activation of NAMPT by H247-phosphorylation causes stabilization of the enzyme-phosphoribosylpyrophosphate complex, permitting efficient capture of NAM. Reactant and product structures establish reaction coordinate motion for NAMPT to be migration of the ribosyl anomeric carbon from the pyrophosphate leaving group to the nicotinamide-N1 while the 5-phosphoryl group, the pyrophosphate moiety, and the nicotinamide ring remain fixed in the catalytic site.